I picked it up for $5 on Steam this week and it's fun for an hour or so. Granted, I'm spoiled by the greatness of MW2, so Shattered Horizons seems pretty dull to me. An FPS with only one weapon is just not cutting it, but it was $5 so no great loss.
Others might really like it, though. MW2 has ruined all other FPS games for me unfortunately...